Rota-Baxter algebras were introduced to solve some analytic and combinatorial problems and have appeared in many fields in mathematics and mathematical physics. Rota-Baxter algebras provide a construction of pre-Lie algebras from associative algebras
. In this paper, we give all Rota-Baxter operators of weight 1 on complex associative algebras in dimension $leq 3$ and their corresponding pre-Lie algebras.
